The invention concerns an apparatus for treatment of liquids wherein the liquids flow through a porous web material. The type of porous web material depends on the treatment to which the liquid is to be subjected. The treatment can be a filtration process, for example, to remove particles, an adsorption process wherein specific components are removed from the liquid by adsorption onto the web material, or a catalytic process wherein one or more components of the liquid are subjected to specific chemical or physical conversions by contact with the porous web material.
Appropriate porous web materials include microporous membranes with a pore size range from 0.05 to 15 .mu.m or nonwoven fibers. When the liquid is to be treated by filtration, suitable web materials include inert microporous membranes made from polymers such as cellulose acetate, regenerated cellulose, polyamides, polysulfone, polyethersulfone, etc., or nonwoven membranes made from polymers such as polyester, polypropylene and cellulose fibers. In the case of adsorption, adsorption membranes are used. Adsorption membranes are membranes that carry functional groups, ligands, or reactants on their inner and/or outer surface that are capable of interacting with at least one substance of a liquid phase that is in contact with them, and the term may be applied to a wide variety of adsorption membranes such as cationic, anionic, ligand, affinity or activated membranes which, in turn, may be classified according to the type of functional groups, ligands, or reactants they possess. Catalytic processes preferably involve enzymatic conversions wherein immobilized enzymes are on the porous web material. Acid- or base-catalyzed conversions, however, are also possible using strongly acid or strongly basic membrane ion exchangers membranes.
The porous web material can be used in either one layer or in several layers. The multilayer version can be formed into a hollow cylinder with an internal and external support element, wherein tangential channels may be in the form of annular gaps or as rectangular mats, the latter being the preferred form for smaller disposables used on a laboratory scale. The tangential channels can also contain a tangentially permeable support structure, consisting of, for example, a woven fabric. Devices using such porous web materials can also have several porous webs and tangential channels, wherein a feed channel in the porous web material and a discharge channel are arranged in alternation. The latter arrangement is preferably implemented so that, for purposes of axial flow, two webs of the web material are wound together with two webs of the support structure around a core, and the support structure forming the discharge channel is connected on the feed side fluid-tight to the adjacent porous webs. The same is then done on the discharge side, with the support structure forming the feed channel.
There are devices known for the treatment of liquids wherein pressurized liquid feeds are fed to a flat, porous web material via a tangential channel closed on the end, passed through this material and then discharged through another tangential channel that has an opening on the other end of the device. The shortcomings of such devices are that they have unnecessarily large dead volumes and the applied operating pressure is only partially utilized for permeation of the web material--a situation that is accompanied by different permeation-active pressure differences over the length of the channel. A large dead volume is a drawback because, among other things, it increases the manufacturing costs of the apparatus. Incomplete utilization of the operating pressure leads to inefficiency, while locally different permeation-active pressure differences tend to lead to more rapid blinding in most applications in the range of higher pressure differentials, and to nonuniform target substance breakthrough or nonuniform substance conversion during adsorption and catalysis, respectively.
The primary goal of the present invention is therefore to provide an apparatus for the treatment of liquids of the type mentioned that avoids excessive dead volume, and wherein the employed operating pressure is utilized as completely as possible for permeation of the liquids through the porous web material.